Highly efficient bipolar host material based-on indole and triazine moiety for red phosphorescent light-emitting diodes

摘要

Two novel indole-based, bipolar, host materials were designed and synthesized by introducing the triazine unit to the 5-position of indole moiety with a meta-linking strategy. The two host materials exhibited excellence bipolar transport abilities and the meta-linking analog presented a high T-g value (>120 degrees C). Furthermore, their electrochemical and photo-physical properties were also fully characterized and all the results exhibited that the meta-linking strategy made a significant effect on the physical properties of the two hosts. Moreover, the PHOLED devices using 9-(4-(5-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1H-indol-1-yl) phenyl)-9H-carbazole and 9-(4-(5-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-1H-indol-1-yl)phenyl)-9H-carbazole as hosts were also fabricated to evaluate the practical utilities of host materials. The devices achieved the maximum external quantum efficiencies of 17.53% for para-linking compound and 14.53% for meta-linking analog, respectively. In particular, para-linking compound based device revealed the maximum external quantum efficiency was twice that of the device using 4,4'-bis(N-carbazolyl)-1,10-biphenyl as the host. (C) 2015 Elsevier Ltd. All rights reserved.